The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As is known in itself, an aircraft engine, 17 as illustrated in FIG. 8, which is generally of the turbojet engine type, is placed inside a nacelle 7 which, among other functions:                provides an aerodynamic fairing for the engine,        makes it possible to channel the outside air toward the engine,        makes it possible to connect the engine to the aircraft.        
Traditionally, a cascade thrust reverser comprises two half-cowls 19 each slidingly mounted on a longitudinal support half-beam called the 12 o'clock beam 1 generally pivotably mounted on a support mast of the nacelle.
The rotational movement of each half-beam on the nacelle support thus makes it possible to pivot each half-cowl 19 relative to that mast 13 for maintenance operations.
A lower support beam also exists called the 6 o'clock beam 5 comprising two half-beams capable of opening by pivoting with the half-cowls 19 and therefore generally equipped with means for connecting to each other and locking the two half-structures.
Each 6 o'clock half-beam 5 is traditionally connected to the corresponding 12 o'clock 1 half-beam by means of an inner structure surrounding the turbojet engine 17.
Depending on the design of the nacelle, the 12 o'clock beam may be stationary and the opening of the half-cowls for maintenance purposes may be done by completely translating said sliding cowls. In that case, it is also possible to provide a single substantially peripheral moving cowl, in which case the 6 o'clock beam is then no longer present.
The support structures or beams are generally also equipped with guide rails allowing each half-cowl to slide on its associated half-beam alternating between a thrust reverser position called the direct jet position and a thrust reverser position called the reverse jet position.
Thus, traditionally, each 12 o'clock half-beam will have a structure, on its outer face, of primary and secondary rails able to allow the movement of the associated half-cowl 19, and multiple hinge yokes capable of allowing the half-beam to be articulated on the associated nacelle mast.
The 12 o'clock and 6 o'clock beams are connected to each other by a substantially annular structure called the front frame and generally formed by two front half-frames 3 each extending between said corresponding half-beams on either side of the middle plane of the nacelle.
This front frame is designed to be fastened to the periphery of the downstream edge of a casing of the fan of the engine 17, and thereby to contribute to the reaction and transmission of forces between the different parts of the nacelle 7 and the turbojet engine 17.
Furthermore, in the case of a nacelle equipped with a cascade thrust reverser device, the front frame also serves to support said vanes of the thrust reverser.
The connection of each 12 o'clock-beam with its associated front frame part is done by means of a mounted or integrated extension (for example, see document FR 2,920,192) on the upstream part (relative to the direction of airflow in the nacelle) of the half-beam, and intended to cooperate by snapping with a corresponding receptacle of the front frame. This receptacle of the front frame is traditionally called “ash pan”.
Once this snapping is done, rivets are fastened to secure the extension of the beam with the wall of the front half-frame.
The 6 o'clock half-beams have substantially the same structure, with the exception that they do not comprise hinge yokes, but locking yokes and/or corresponding locking means.
Such an assembly method is not fully satisfactory, on the one hand because it only allows forces to pass over part of its section, and on the other hand because the fasteners, for example rivets, are mounted blind (i.e., they are only accessible from the outside), which makes them complicated to assemble and monitor.
In particular, by using such an assembly method, the working junction area substantially represents only half of the total height of the assembly.
Furthermore, the more frequent use of composite materials, in particular to produce part or all of said beams and/or front frame, raises issues regarding the relative orientation and the continuity of the fibers of the materials relative to one another so as to optimize the passages of forces and strength.
Various applications have sought to provide solutions to these drawbacks. Examples in particular include published PCT application WO/2011/135213.
WO/2011/135213 targets a support half-structure for an aircraft engine nacelle, comprising at least one longitudinal beam and one front half-frame, remarkable in that said beam and said half-frames are made from composite materials, in the said front half-frame has an open section, and in that said beam and said front half-frame form a single piece.
By producing a single-piece part in a single molding operation (using known RTM (Resin Transfer Molding) or infusion techniques, for example), continuity of the fibers of the composite materials is obtained, between the beam and its associated front half-frame: in this way, improved transmission of forces between those two members is obtained.
By placing the fibers in an optimized way (in the direction in which the forces pass), mass savings are achieved relative to an aluminum block.
Furthermore, in the case of such a single-piece part, no fastening means between the members are of course necessary, which makes it possible to eliminate the aforementioned assembly and monitoring problems.
The invention also makes it possible to move the junction between the beam and its associated front half-frame further away from the very charged transition zone between the (substantially vertical) 12 o'clock web of the beam and its front half-frame, by lengthening the extension of the beam (or the front half-frame, depending on the considered alternative).
According to one method for manufacturing a single-piece integrated front frame beam, this assembly is designed so as to be configurable from subassemblies assembled together to form a preform before polymerization and final treatment, thereby making the part a single piece.
More particularly, the beam structure substantially forms an L comprising a longitudinal web and a sole generally in the shape of an omega.
The front frame is integrated into a web and is attached on the structure of the beam at one upstream lateral end of the omega-shaped floor by means of right-angled returns glued to the beam structure. This same web will also be assembled by fastening as well as with a connecting flange connecting the front frame to the fan casing.
In general, many subassemblies are assembled using right-angled end returns.
At these connections, and in particular therefore at the web that is connected to the front frame transmits the forces from said front frame directly to the mast, in particular using an upstream connecting yoke; the forces therefore follow a transmission line in which the carbon fibers are curved at 90°. Such force transmission lines are not optimal.
The front frame creates torsion and traction forces on the beam. Currently, the forces pass through perpendicular webs.
The flange for connecting to the fan casing creates a significant traction force on the beam. Currently, the forces pass through perpendicular webs, and only through the omega-shaped floor of the beam.
Thus, it appears that the sole criterion of continuity of the fibers was not sufficient and that it was necessary to be able to still further improve the transmission of forces within such a nacelle support structure.